Resetting quotas en masse

I will soon be implementing quotas at the postoffice level, where I had no quota restriction before. I have some users who have individual quotas set. Will setting the quota on the postoffice reset the individual quotas?

If not, is there any way to reset those individual quotas back to defaults without doing them one by one?

Is there any way (gwcheck maybe?) to find out who has an individual quota set?